bug#50207: 28.0.50; ansi-color-compilation-filter and rgrep

[Juri Linkov]

>> - (add-hook 'compilation-filter-hook #'ansi-color-compilation-filter)
>
> I encountered this a bit ago, and did a bit of diagnosis, but it ended up
> on my back-burner. I think the issue is due to how the
> compilation-filter-hooks for grep and ansi-color interact. `grep-filter' is
> fairly simple and wants to see both the start and end of an ANSI-colorized
> region, so it "rewinds" to the beginning of a line every time it's
> called. `ansi-color-compilation-filter', on the other hand, is smart enough
> to handle the case where it only sees the start of a colorized region in
> one call, and the end in the next call (see `ansi-color-context' for
> details).

Would it be possible to solve the problem by adding a new buffer-local
variable (disabled by default) that will enable line mode for
`ansi-color-compilation-filter' so that it will handle only complete lines
like grep mode does?